Recently, secondary batteries have been widely used in devises ranging from large devices such as automobiles and power storage systems to small devices such as mobile phones, camcorders, and lap-top computers.
Lithium secondary batteries have been used as secondary batteries because lithium secondary batteries have a larger capacity per unit area than that of nickel-manganese batteries or nickel-cadmium batteries.
However, conventional lithium secondary batteries can be easily overheated, have a low energy density of about 360 Wh/kg, and have a relatively low battery output, and thus, are not suitable as a next-generation battery for a vehicle.
Subsequently, an all-solid-state lithium ion battery having a higher output and a higher energy density has been developed.
The all-solid-state lithium ion battery includes: a cathode having an active material, a solid electrolyte, a conductive material, a binder, and the like; an anode; and a solid electrolyte interposed between the cathode and the anode.
The solid electrolyte is classified into an oxide-based electrolyte and a sulfide-based solid electrolyte. Since the sulfide-based solid electrolyte has a higher lithium ion conductivity than that of the oxide-based solid electrolyte and is stable in a wide voltage range, the sulfide-based solid electrolyte is more widely used.
The cathode may use sulfur as an active material, and may include a sulfide-based solid electrolyte. For example, in a related art, a lithium secondary battery uses a nitrile butadiene rubber (hereinafter, referred to as ‘NBR’) as a binder which binds an electrode material. Since the existing lithium secondary batteries do not use a sulfide-based compound, the NBR can be used.
However, since the all-solid-state lithium ion batteries include the sulfide-based solid electrolyte, the NBR causes a chemical reaction. Accordingly, when charge and discharge of the battery are repeated, the NBR may harden. The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.